1. Field of the Invention
The present invention is directed to interlocking wall panels, and more specifically to a composition of matter and physical structures to enhance thermal stability and reduce rattling, warpage and buckling. The prior art is generally found in Class 52.
2. Description of the Prior Art
The prior art is exemplfiied by the following patents: U.S. Pat. Nos. 3,621,625; 3,783,570; 4,070,843; 4,102,106; 4,223,490 and West German Pat. No. 24 40 497. These previous patents have disclosed various methods of interlocking wall and roof panels. However, they have contributed little to the problems arising from thermal expansion and contraction after installation.
In particular, U.S. Pat. No. 4,223,490 discloses panels that interlock via a tongue and groove arrangement and that have breakable pins for preventing the tongue from fully penetrating the groove during installation. Overcoming the thermal expansion is a critical factor in the marketability of this product because the panels will expand as much as 5/8 of an inch over the 40 inch length at temperatures of 160.degree. F., which is easily attainable on hot sunny days. This expansion must be dealt with to prevent the panels from buckling away from the wall on which it is mounted. Then, upon thermal expansion after installation the expanding tongue breaks off the breakable pins and is able to penetrate farther into the groove, and upon contraction the tongue partially withdraws from the groove. This system of interlocking the panels, however, still has a problem of rattling due to the looseness of the tongue and groove joint. Also, the breakable nature of the pins may lead to a substantial number of the pins being broken off during shipment of the panels . This leads to misalignment of the panels upon installation and aggravates the rattling problem.
Similarly, U.S. Pat. No. 4,070,843 has a short tongue and a wide groove interlock, but primarily relies upon the nailing of the panels to the roof or wall for stability. No compensation for thermal expansion is really provided, and rattling due to the loose nature of the interlock is likely.
U.S. Pat. No. 3,073,570 provides a deep tongue and groove interlock, but fails to provide any expansion or contraction looseness so upon thermal expansion one would expect the panels to buckle.
The interlock of U.S. Pat. No. 4,102,106 is essentially a tongue and groove with the groove being the space between a panel and the supporting wall or roof. As with the previous patents, the tongue and groove interlock is loose, and also no compensation for thermal expansion or contraction is provided.
Lastly, West German Pat. No. 24 40 497 has an interlock similar to U.S. Pat. No. 4,102,106. And U.S. Pat. No. 3,621,625 has an interlock formed by again a tongue and groove but with the tongue wedging into the groove. However, no compensation for thermal expansion or contraction is provided, and thus one would anticipate buckling upon expansion and a loose interlock upon contraction resulting in rattling.